This invention relates to a digital display system for electronic desk-top calculators, and more specifically to a dynamic (pulse lighting) display system for lighting display devices in a time-sharing manner.
Generally, digital display systems are classified into static and dynamic display types. For electronic desk-top calculators and the like, the classic static systems are being supplanted by the dynamic display types which permit reduction in the numbers of decoder circuits, drive circuits, etc., that the static type require for each of the digits of the numbers to be handled. The dynamic display system, which takes advantage of the afterimage effect of the human eyes, sequentially lights a plurality of display devices with pulses in a time-sharing manner, thereby reducing the overall number of decoder and drive circuits to a quantity which is just enough for one digit. For this purpose, it is important to establish accurate synchronism between the timing pulses (timing signals) and display signals for pulse lighting the display devices. Actually, however, the lag of display signals due to their passage through the decoder and drive circuits, etc., and the lag of timing signals due to their passage through buffer circuits, etc., have presented the problem of imperfect synchronism between the display and timing signals. The imperfect synchronism in turn causes flicker (double lighting) of the display devices. The flicker also stems from overlapping of the display signals.